Mine working condition adaptive gradient aluminum medium manganese steel and preparation method and application thereof

Abstract

A mine working condition adaptive gradient aluminum medium manganese steel, a preparation method and application thereof, according to mass percentage, C 0.25~0.35%, Mn 5.5~8.5%, Si 0.4~0.8%, P≤0.01%, S≤0.01%, Al 0.8~4.5%, the balance being Fe and inevitable impurities; Al is differentially designed according to 0.8~1.2%, 1.8~2.2% and 3.8~4.5%, so as to realize accurate performance targeted matching of different Al content steel bodies to different service positions of mines; the preparation method comprises smelting and composition control, gradient adaptive rolling and performance targeted heat treatment, and the tempering temperature is negatively correlated with the Al content; without adding valuable alloy elements, the toughness, wear resistance and corrosion resistance of the medium manganese steel are synergistically improved, and the medium manganese steel can be widely applied to key wear-resistant and corrosion-resistant components such as mine crushing equipment lining plate, shovel blade edge of shovel equipment, mine support bracket and the like.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical materials technology, specifically relating to a gradient aluminum-manganese steel adapted to mining conditions, its preparation method, and its application. Background Technology

[0002] Medium manganese steel, due to its combination of high strength, high toughness, and transformation-induced plasticity (TRIP) effect, has become a core candidate material for key wear-resistant components in mining equipment. Mining conditions have significant multi-part differentiated service characteristics: the bucket cutting edge needs to withstand high abrasion and impact loads, the mining support needs to balance low-temperature toughness and corrosion resistance, and the bucket sidewall requires a balance of strength and plasticity as well as fatigue resistance.

[0003] Currently, performance control of medium-manganese steel mainly focuses on optimizing the content of single elements or improving general processes. Chinese patent CN121592961A discloses a high-alumina, medium-manganese lightweight wear-resistant steel and its preparation method, wherein C 0.8~1.3%, Mn 8.0~14.0%, Al... The steel contains 2.0-4.5% Al, and includes various precious alloying elements such as Mo, W, Cr, Zr, and Ti. Existing technologies disclose a single fixed Al content of 2.0-4.5% in medium-manganese steel, but this has a narrow Al range, significant differences in C / Mn content and alloy system. This application, however, targets and adapts the steel to three gradient ranges from 0.8% to 4.5%, using a gradient design to match different working conditions with different compositions. Higher Al content corresponds to lower tempering for differentiated heat treatment. While existing technologies add multiple elements such as Mo, W, Cr, Zr, and Ti, this application requires no addition of any precious alloying elements and is specifically adapted to mining conditions such as bucket sidewalls, supports, and bucket cutting edges. This application solves the technical problem that traditional medium-manganese steel cannot adapt to all working conditions when multiple components are used in mining applications, achieving beneficial effects such as controllable cost, precise performance matching, and balanced component lifespan. The technical problem solved is unique, and the technical solution is not obvious. Chinese patent CN120758805A discloses a 1000 MPa-grade low-density medium-manganese steel and its preparation method, wherein C 0.80~0.95%, Al 7.50~9.30%, Mn 8.35~12.87%, is suitable for automotive lightweighting. Existing technologies disclose the addition of high Al content to medium-manganese steel, but the application field is automotive, not mining conditions. Chinese patent CN121362920A discloses a 1300MPa-grade ultra-low yield strength ratio medium-manganese high-strength steel plate and its manufacturing method, wherein C... 0.1~0.2%, Mn 3~7%, Al≤0.1%, containing Cr, Nb, V, Ti, with an upper limit of Al content of only 0.1%, which does not overlap with the Al content range of this invention; for example, patent CN118460931A discloses a medium manganese steel with high corrosion resistance and high yield strength, its preparation method and application, which improves corrosion resistance by controlling carbide precipitation through two-phase annealing; patent CN118422057A discloses a medium manganese steel with good impact abrasive wear performance, which improves impact wear performance by adding precious alloying elements such as Nb, V, Cr, Ni to the medium manganese steel; patent CN118166262A discloses the preparation of low-cost high carbon medium manganese steel for mining and high impact load environments, which develops high carbon medium manganese steel for high impact loads in mining, but the Al content is extremely low and is not designed as an alloying element, Al is only added as a deoxidizer (0.1~0.4%). However, existing technologies have the following core flaws: 1. Lack of working condition targeting in composition design: Existing medium manganese steel with aluminum addition technology mostly adopts a fixed aluminum content (such as 1.5%~2.5%), without differentiated design for the performance requirements of different components in the mine. As a result, a single component steel cannot simultaneously meet the requirements of high wear resistance of bucket cutting edge, low temperature flexibility of support and strong plastic balance of sidewall. 2. Insufficient performance synergy: Conventional medium manganese steel is prone to the contradiction that "increased wear resistance leads to decreased toughness, and enhanced corrosion resistance leads to insufficient strength." For example, although high-aluminum medium manganese steel has excellent corrosion resistance, its impact energy at -40℃ will be significantly reduced; low-aluminum steel has a balanced strength and toughness, but its wear resistance and corrosion resistance cannot meet the long-term service requirements of harsh mining environments. 3. Lack of gradient performance matching: The service load and failure modes of different components of mining equipment vary significantly. However, the existing technology has not established a correspondence between composition gradient and performance gradient, making it impossible to achieve precise matching of "component-performance-composition". This results in low material utilization and uneven overall service life of the equipment.

[0004] Furthermore, some technical solutions introduce expensive alloying elements such as Cr and Ni to balance multiple performance aspects (e.g., CN118422057A adds 1.2% Cr and 1.3% Ni), significantly increasing production costs and failing to meet the low-cost requirements of mining equipment. Therefore, developing a medium-manganese steel based on gradient aluminum content design, adaptable to the differentiated needs of various mining components, and possessing both strength, toughness, wear resistance, and corrosion resistance has become an urgent technical challenge.

[0005] 4. Furthermore, existing methods for preparing medium-manganese steel are mostly general-purpose processes that fail to differentiate based on different alloy compositions. This results in high-aluminum-content steels sacrificing low-temperature toughness while improving wear resistance, while low-aluminum-content steels struggle to meet the demands of high-abrasion conditions. Therefore, there is an urgent need to develop a medium-manganese steel with integrated composition, process, and performance design, along with its preparation method and applications, to achieve precise performance adaptation for various components in mines. Summary of the Invention

[0006] Technical problem to be solved: The technical problem to be solved by the present invention is to overcome the technical defects of existing medium manganese steel for mining, such as no gradient design of composition, poor performance synergy, and high cost, and to provide a gradient aluminum medium manganese steel adapted to mining conditions, its preparation method and application.

[0007] Purpose of the invention: To address the technical shortcomings of existing medium-manganese steel for mining, such as lack of gradient design in composition, poor performance synergy, and high cost, the present invention aims to provide a gradient aluminum medium-manganese steel adapted to mining conditions, its preparation method, and its application. By precisely controlling the gradient aluminum content from 0.8% to 4.5%, combined with a matching heat treatment process, the performance of steel bodies with different aluminum contents can be targeted and matched to different service components in the mine. At the same time, without adding expensive alloying elements, it achieves a synergistic improvement in strength, toughness, wear resistance, and corrosion resistance, thereby reducing production costs and extending the overall service life of mining equipment.

[0008] The technical solution is a gradient aluminum-manganese steel adapted to mining conditions. Its chemical composition, by mass percentage, includes: C: 0.25~0.35%, Mn: 5.5~8.5%, Si: 0.4~0.8%, P≤0.01%, S≤0.01%, Al: 0.8~4.5%, with the balance being Fe and unavoidable impurities. The Al content is differentially controlled within three gradient ranges from 0.8% to 4.5%. By differentiating the mechanical properties, wear resistance, and corrosion resistance of the steel body through different Al content ranges, the performance of different service components in the mine can be targeted and matched.

[0009] When the Al content is 0.8~1.2%, the steel body is suitable for mining bucket sidewall components that require high strength-plasticity balance and low-temperature toughness.

[0010] Furthermore, when the Al content is 1.8~2.2%, the steel body is suitable for mine support components that require high synergistic performance in low-temperature toughness and impact wear resistance.

[0011] Furthermore, when the Al content is 3.8~4.5%, the steel body is suitable for mining bucket cutting edge components that require high strength, high wear resistance and high corrosion resistance.

[0012] Furthermore, the manganese steel in the mining-condition-adaptive gradient aluminum alloy meets at least one of the following performance indicators: Tensile strength ≥ 877 MPa; Yield strength ≥ 521 MPa; Elongation after fracture ≥26%; Dry sliding friction wear rate at 200 N ≤ 7.64 × 10⁻⁶ -5 mm 3 / (N·m); Charpy V-shaped impact energy at -40℃ ≥41 J; The corrosion weight loss rate after 48 hours of salt spray corrosion was lower than that of aluminum-free medium manganese steel.

[0013] A method for preparing gradient aluminum-manganese steel adapted to mining conditions includes the following steps: S1. Smelting and composition control: The amount of aluminum ingots added is precisely controlled according to the target Al content. The aluminum is smelted in an electric furnace, refined in an LF furnace, and treated in a vacuum with a vacuum degree of ≥70 kPa and a holding time of ≥30 min, so that the Al element is evenly distributed in the molten steel. S2, Gradient Adaptive Rolling: The billet is placed in a regenerative heating furnace, preheated to 850℃ at a rate of ≤85℃ / h, and then heated to 1150~1160℃ and held for 2~4 h. It is then rolled in the high-temperature austenitic region with an initial rolling temperature ≥1090℃ and a final rolling temperature ≥920℃. The austenitic grains are refined by temperature and rolling control. S3, Performance-targeted heat treatment: Quenching temperature ≥850℃, cooling to <100℃ and water removal with reddening temperature <200℃; The tempering temperature should be adjusted according to the Al content, and the temperature should be maintained for 4-8 hours before air cooling to room temperature. The principle for adjusting the tempering temperature is: the higher the Al content, the lower the tempering temperature.

[0014] Furthermore, the tempering temperature mentioned in step S3 is: When the Al content is 0.8~1.2%, the tempering temperature is 200~220℃; When the Al content is 1.8~2.2%, the tempering temperature is 190~210℃; When the Al content is 3.8~4.5%, the tempering temperature is 170~190℃.

[0015] Furthermore, the vacuum degree of the vacuum treatment in step S1 is ≥70 kPa and the holding time is ≥30 min, which is used to remove gas and trace impurities in the molten steel and promote the uniform distribution of Al elements in the steel matrix, so as to avoid the formation of inclusions and agglomeration under high Al content.

[0016] Furthermore, the heating rate of the preheating section in step S2 is controlled at ≤85℃ / h to prevent the billet from cracking due to thermal stress and to ensure the uniformity of the microstructure of the high Al content steel body.

[0017] This application also discloses the application of gradient aluminum-manganese steel adapted to mining conditions in key components for multiple mining conditions, wherein the key components for multiple mining conditions are liners for mining crushing equipment, cutting edges of buckets for shovels and conveyors, or mining support brackets.

[0018] Explanation of Principle: This invention belongs to the technical field of wear-resistant and corrosion-resistant steel materials. It discloses a gradient aluminum medium-manganese steel adapted to mining conditions, its preparation method, and its application. The aim is to solve the technical problem that existing medium-manganese steel cannot simultaneously achieve high toughness, wear resistance, and corrosion resistance under various mining conditions. The gradient aluminum medium-manganese steel uses medium-manganese steel as the matrix, and its basic composition by mass percentage is: C: 0.25~0.35%, Mn: 5.5~8.5%, Si: 0.4~0.8%, P≤0.01%, S≤0.01%, with the balance being Fe and unavoidable impurities. By introducing 0.8~4.5% Al, the performance of steels with different Al contents is targeted to different service parts in the mine. Performance tests show that the tensile strength of the aluminum-free original steel is 857 MPa, while the tensile strengths of the 0.8~1.2% Al, 1.8~2.2% Al, and 3.8~4.5% Al steels are increased to 877 MPa, 902 MPa, and 956 MPa, respectively. Under dry friction conditions of MPa and 200 N, the wear rate of 3.8–4.5% Al steel is as low as 4.38 × 10⁻⁶. -5 mm 3 / (N·m), a decrease of 51.5% compared to the original steel; in the salt spray corrosion test, the higher the Al content, the better the corrosion resistance. 1.8~2.2% Al steel takes into account the impact energy (41 J) at -40℃ and the high elongation (27%), and is suitable for mine support components. 3.8~4.5% Al steel is suitable for highly abrasive parts such as bucket cutting edges. This invention achieves differentiated matching of steel performance through gradient Al content design, meets the composite service requirements of multiple mine components, has controllable cost and high industrial feasibility, and can be widely used in key wear-resistant and corrosion-resistant components of mine crushing and shoveling equipment.

[0019] This application provides a gradient aluminum-manganese steel adapted for mining conditions, its preparation method, and its application, which has the following beneficial effects: 1. Strong adaptability to specific working conditions: Through a gradient aluminum content design of 0.8% to 4.5%, the steel with different Al contents achieves precise performance matching for different mining components (bucket sidewalls, mining supports, bucket cutting edges), solving the problem that traditional medium manganese steel, with its single composition, cannot meet the needs of multiple components. The Al 1% sample achieved an impact energy of 132 J at -20℃, an increase of 53.49% compared to steel without Al, making it suitable for mining support components requiring low-temperature toughness; the Al 4% sample had a dry sliding friction wear rate as low as 4.38×10⁻⁶ at 200N. -5 mm 3 / (N·m), a reduction of 51.5% compared to Al-free steel, and a 48h salt spray corrosion rate of only 22.12% of that of Al-free steel, making it suitable for highly abrasive and corrosive parts such as bucket cutting edges; 2. Excellent performance synergy: The high Al content (3.8~4.5%) steel body has a tensile strength of 956 MPa, which is 11.55% higher than that of aluminum-free steel. The dry friction wear rate is reduced by 51.5%, and the corrosion rate after 48 hours of salt spray corrosion is only 22.12% of that of aluminum-free steel, achieving a synergistic improvement in strength, toughness, wear resistance, and corrosion resistance. The medium Al content (1.8~2.2%) steel body achieves the best balance between low-temperature toughness and impact wear resistance. The impact energy at -40℃ is maintained above 41 J, while the sand friction wear rate is the lowest (1.821×10). -4 mm 3 / (N·m)), which balances low-temperature toughness and impact wear resistance; 3. Deep synergy between preparation method and composition: By adopting a differentiated heat treatment design that "the higher the Al content, the lower the tempering temperature", the technical problem of low-temperature toughness decreases under high Al content is overcome, and the integrated synergistic control of composition, process and performance is achieved. 4. Controllable production costs: No need to add precious alloying elements such as Cr and Ni. The cost per ton of steel is 8% to 12% lower than that of medium manganese steel containing Cr and Ni. The cost reduction is even more significant than that of multi-element alloy medium manganese steel containing Mo, W, Cr, Zr and Ti (such as CN121592961A). 5. High feasibility for industrialization: The preparation process uses conventional equipment and can be directly connected to existing steel production lines, facilitating large-scale mass production. Attached Figure Description

[0020] Figure 1 Comparison of metallographic structures (200x magnification) of manganese steel with different Al contents according to this invention; wherein, Figure 1 In the middle (a) is the comparative example (without Al), the grains are coarse (average grain size is about 50 μm) and the carbide is unevenly distributed; Figure 1 (b) is Example 1 (Al 1%), with refined grains and uniform carbide distribution; Figure 1 (c) is Example 2 (Al2%), with further grain refinement (average grain size ≤25 μm); Figure 1 In the middle (d), which is Example 3 (Al 4%), the average grain size is ≤20 μm, the carbides are finely dispersed, and a thin and dense oxide film is visible on the surface; Figure 2 These are comparative images of the macroscopic morphology of manganese steel with different Al contents after 48 hours of salt spray corrosion according to the present invention; wherein, Figure 2 In the middle (a) is the comparative example (without Al), the surface is completely covered with dense rust spots, and 80% of the area shows severe rust peeling; Figure 2 (b) is Example 1 (Al1%), with approximately 60% of the area heavily corroded, and the degree of corrosion is reduced compared to the comparative example; Figure 2(c) represents Example 2 (Al2%), where only 40% of the area has severe corrosion, while the main area remains flat; Figure 2 The middle (d) is Example 3 (Al4%), with only slight surface rust in some areas, no rust peeling, and the best surface integrity. Detailed Implementation

[0021] To make the technical solution, objective, and beneficial effects of the present invention clearer, the preparation and performance of the manganese steel in the mine-condition-adaptive gradient aluminum of the present invention will be described in detail below with reference to specific embodiments and comparative examples. Unless otherwise specified, the experimental methods used in this embodiment are conventional methods in the metallurgical field, and the equipment used is commercial standard equipment, which can be obtained by those skilled in the art through conventional commercial channels.

[0022] I. Experimental Raw Materials and Equipment 1. Raw material composition In this invention, the basic chemical composition (mass percentage) of manganese steel is uniformly as follows: C: 0.30%, Mn: 7.0%, Si: 0.6%, P: 0.008%, S: 0.007%, with the balance being Fe and unavoidable impurities. By adjusting the amount of Al added, medium manganese steel samples with no Al (comparative example), 1% Al content (Example 1), 2% Al content (Example 2), and 4% Al content (Example 3) were prepared respectively. The Al element was precisely added during the smelting stage in the form of aluminum ingots.

[0023] 2. Main experimental equipment (1) Smelting: Scrap steel, ferrosilicon and ferromanganese are added according to the basic composition, and then heated to 1560℃ in a vacuum induction melting furnace. Aluminum ingots are added according to the target Al content. After holding for 20 min, the mixture is transferred to an LF furnace for refining. After heating to 1660℃, vacuum treatment is performed (vacuum degree 80 kPa, held for 35 min). The ingots are cast into 120 mm × 80 mm × 60 mm. (2) Rolling: The billet is fed into a regenerative heating furnace and heated to 850°C at 75°C / h, and then heated to 1160°C and held for 3 hours; the tapping temperature is 1150°C, the initial rolling temperature is 1100°C, the final rolling temperature is 925°C, and it is rolled into an 8 mm thick plate. (3) Heat treatment: Quenching temperature 855℃, cooling to 95℃ and then water removal (redness temperature 185℃); Tempering temperature: 220℃ for comparative example (no Al) and Example 1 (Al 1%), 210℃ for Example 2 (Al 2%), and 180℃ for Example 3 (Al 4%). All were held at this temperature for 6 hours and then air-cooled to room temperature. The mechanical property testing equipment used in this application includes: WDW-1000 electronic universal tensile testing machine and JB-300B Charpy pendulum impact testing machine. The wear performance testing equipment used in this application includes: MM-2000 friction and wear testing machine (dry friction, sand friction) and MLD-10 impact wear testing machine; The corrosion resistance testing equipment used in this application is: YWX / Q-250 neutral salt spray test chamber (5% NaCl solution, pH=6.5~7.2, temperature 35℃).

[0024] II. Sample Preparation Process All samples were prepared using a standardized process, with the temperature adjusted only during the tempering stage based on the Al content. 1. Smelting and refining: Scrap steel, ferrosilicon, and ferromanganese are added according to the basic composition and heated to 1560℃ in a vacuum induction melting furnace. Aluminum ingots are added according to the target Al content. After holding at this temperature for 20 min, the mixture is transferred to an LF furnace for refining. The temperature is raised to 1660℃ and then vacuum treated (vacuum degree 80 kPa, held for 35 min). The mixture is then cast into 120 mm × 80 mm × 60 mm ingots. The residual heat from casting is used to cut the billet to a thickness of 40 mm. 2. Heating and rolling: The billet is fed into a regenerative heating furnace, loaded at 320°C, heated to 850°C at 75°C / h (preheating section), then heated to 1160°C and held for 3 hours (heating section), and tapped at 1150°C; it is rolled in the high-temperature austenitic region, with an initial rolling temperature of 1100°C and a final rolling temperature of 925°C, to produce 8 mm thick plates; 3. Performance-targeted heat treatment: Quenching temperature 855℃, cooling to 95℃ and then water-cooled (returning temperature 185℃); tempering temperature is adapted according to Al content, and the selection criteria are as follows: 220℃ is used for the comparative example (no Al) and Example 1 (Al 1%) to retain sufficient low-temperature toughness and avoid brittleness caused by excessively low tempering temperature; 210℃ is used for Example 2 (Al 2%) to balance impact wear performance and low-temperature toughness, so as to minimize the sand friction wear rate; 180℃ is used for Example 3 (Al 4%) to promote the dispersion precipitation of carbides and the formation of a dense passivation film, improve wear resistance and corrosion resistance, and at the same time avoid the destruction of the passivation film caused by excessively high tempering temperature; all are held at this temperature for 6 hours and then air-cooled to room temperature.

[0025] III. Performance Testing Methods 1. Tensile properties: Prepare standard tensile specimens with a gauge length of 50 mm according to GB / T 228.1-2010, and test the tensile strength, yield strength and elongation after fracture at a tensile rate of 1 mm / min. 2. Impact performance: Prepare 10 mm × 10 mm × 55 mm V-notch specimens according to GB / T 229-2020, and test Charpy impact energy at room temperature (25℃), -20℃, and -40℃ respectively; 3. Wear performance Dry sliding friction: load 200 N, grinding workpiece GCr15 steel ring (hardness 58 HRC), rotation speed 200 r / min, wear time 2 h, calculate volumetric wear rate; Sand friction: Based on dry friction, 40-mesh quartz sand (flow rate 360 ​​g / min) was introduced, and the volumetric wear rate was tested; Impact wear: Tested at impact energies of 1 J, 2 J and 4 J respectively, with an impact frequency of 1 Hz and a wear time of 1 h, and the volumetric wear rate was statistically analyzed. 4. Salt spray corrosion performance: The sample was cut into 50 mm × 50 mm × 5 mm pieces, and after grinding, cleaning, drying and weighing, it was exposed in a salt spray chamber for 2 h, 6 h, 12 h, 24 h and 48 h respectively. After removal, the corrosion products were removed and the sample was weighed again. The corrosion rate at different time periods was calculated.

[0026] IV. Performance Test Results of Examples and Comparative Examples 1. Mechanical property test results .

[0027] As shown in Table 1: With increasing Al content, the tensile strength, yield strength and elongation after fracture of medium manganese steel show an increasing trend. In Example 3 (Al 4%), the tensile strength increased by 11.55%, the yield strength increased by 39.34%, and the elongation after fracture increased by 42.86% compared with the comparative example, which reflects the solid solution strengthening and grain refinement effect of Al element. The low-temperature impact toughness shows a trend of "first increasing and then decreasing". The impact energy at -20℃ of Example 1 (Al 1%) is increased by 53.49% compared with the control example, and the impact energy at -40℃ is increased by 17.07%. However, the low-temperature impact energy of Example 3 (Al 4%) is significantly decreased, indicating that high Al content will reduce the low-temperature toughness of medium manganese steel, and targeted selection should be made according to the working conditions.

[0028] 2. Wear performance test results Table 2 Comparison of wear properties of manganese steel with different Al contents (unit: mm) 3 / (N·m)) .

[0029] As shown in Table 2: The dry friction wear rate continued to decrease with increasing Al content. The decrease in Example 3 (Al 4%) was 51.5% compared with the comparative example, which was attributed to the increased hardness of the steel substrate and the wear reduction effect of the surface passivation film under high Al content. The abrasive wear rate reached its lowest value (1.821 × 10⁻⁶) at Al 2%. -4 mm 3 / (N·m)), it rises slightly when Al is 4%, because the high Al matrix is ​​prone to brittle spalling under abrasive cutting; Under high impact energy (4J), the higher the Al content, the lower the impact wear rate. In Example 3 (Al 4%), the 4J impact wear rate is only 43.94% of that of the comparative example, which is suitable for high impact erosion conditions in mines.

[0030] 3. Salt spray corrosion performance test results Table 3 Comparison of salt spray corrosion rates of manganese steel with different Al contents (unit: g / m³) 2 ·h) .

[0031] As shown in Table 3: The corrosion rate of all samples showed a trend of "first decreasing and then stabilizing" with the extension of salt spray exposure time. The corrosion rate was highest at 2 h (no stable passivation film on the surface), and the rate tended to stabilize after 12 h. At the same time, the corrosion rate decreased significantly with increasing Al content. In Example 3 (Al 4%), the corrosion rate after 48 hours was only 22.12% of that in the comparative example. This is because Al forms a dense Al2O3 passivation film on the steel surface, which hinders the corrosion of Cl. - It exhibits significant advantages in corrosion resistance against the erosion of the substrate.

[0032] V. Performance Adaptability Analysis of Examples and Comparative Examples 1. Comparative example (without Al): It has balanced mechanical properties but poor wear and corrosion resistance. It is only suitable for low-load conditions without corrosion and cannot meet the requirements of harsh mining environments. 2. Example 1 (Al 1%): It has both excellent strength and plasticity and low temperature toughness. The impact energy at -20℃ reaches 132 J, and the corrosion resistance is improved by 17% compared with the comparative example. It is suitable for components that require low temperature flexibility, such as mine supports and roadway support. 3. Example 2 (Al 2%): Achieves a balance between low-temperature toughness and impact wear resistance, with the lowest sand friction wear rate and an impact energy maintained above 41 J at -40℃, suitable for strong plastic balance components such as bucket sidewalls and conveyor baffles; 4. Example 3 (Al 4%): It has outstanding high strength, high wear resistance and high corrosion resistance. The 4 J impact wear rate and 48 h corrosion rate are the lowest among all groups. It is suitable for high abrasion and high corrosion parts such as bucket cutting edge and crusher liner.

[0033] This invention breaks through the traditional mindset of "fixed aluminum content" in manganese steel, and innovatively designs the Al content into three differentiated gradient ranges (0.8~1.2%, 1.8~2.2%, and 3.8~4.5%), respectively targeting and adapting to the service requirements of different components in the mine.

[0034] Figure 1 The photographing conditions were as follows: the samples were etched with a 4% nitric acid alcohol solution and photographed using a Zeiss Axio Observer A1 metallographic microscope. Key features: the comparative example showed coarse grains (average grain size approximately 50 μm) and unevenly distributed carbides; in Examples 1-3, the grains gradually became finer with increasing Al content, with Example 3 showing an average grain size ≤20 μm and finely dispersed carbides. A thin and dense oxide film was visible on the surface of the 4% Al sample. Technical significance: This directly demonstrates the regulatory effect of gradient Al content on grain refinement and carbide distribution in medium manganese steel, providing microstructural support for improved strength, toughness, and wear resistance, and confirming the technical mechanism that higher Al content leads to more significant grain refinement.

[0035] Figure 2 The shooting conditions were: a 5% NaCl neutral salt spray environment (pH=6.8, temperature 35℃), and corrosion products were not removed after 48 hours of corrosion. The images were taken using a Canon EOS 90D camera under the same lighting conditions (natural light, brightness 500 lux) and the same shooting angle (perpendicular to the sample surface). Key features: The comparative example surface was completely covered with dense rust spots, with 80% showing severe rust peeling; Example 1 showed approximately 60% severe rust on its surface, with a less severe degree of rust compared to the comparative example; Example 2 showed only 40% severe rust on its surface, with the main area remaining relatively flat; Example 3 showed only slight surface rust in some areas, with no rust peeling, exhibiting the best surface integrity. Technical significance: This directly verifies the authenticity of the salt spray corrosion rate data, highlights the significant improvement in corrosion resistance of medium manganese steel by high Al content (especially 4% Al), and proves that the passivation film formed by Al can effectively hinder corrosion, providing a visual basis for service requirements in humid and corrosive mining environments.

[0036] Traditional technologies pursue "optimal" overall performance from a single component, while this invention proposes the opposite approach: "one type of steel is not needed to suit all working conditions." Instead, it uses compositional gradient design to adapt steels with different Al contents to different components, achieving a precise mapping between "component-performance-composition." This shift in thinking is not immediately obvious.

[0037] This application repositions Al (Al) from a traditional deoxidizer or lightweight element as a core element for performance gradient regulation, uncovering a systematic correlation between Al content differences and low-temperature toughness, wear resistance, and corrosion resistance. For the first time, this application systematically reveals that: low Al content is beneficial for retaining low-temperature toughness (impact energy above 48 J at -40℃), medium Al content balances toughness and wear resistance (impact energy 41 J + minimum sand friction wear rate), and high Al content achieves ultimate wear and corrosion resistance (4J impact wear rate reduced by 56% compared to Al-free steel). This systematic revelation surpasses the scattered records of element content-performance relationships in existing literature and represents a substantial creative contribution.

[0038] It is well known in the art that high aluminum content sacrifices low-temperature toughness. However, this application, through a unique synergistic strategy of "higher Al content, lower tempering temperature," enables the 4% Al sample to maintain high strength (956 MPa) while retaining a usable low-temperature impact energy of over 11 J. Although the low-temperature impact energy value is not high, considering the design intent of adapting this composition range to "high abrasion and high corrosion sites," low-temperature impact energy is not its core performance requirement. The technical contribution here lies in breaking through the technical prejudice that "high Al is necessarily unsuitable for harsh mining conditions," and opening up the application possibilities of high Al medium-manganese steel through precise control of process parameters. When mining buckets operate in high-wear and high-corrosion environments, although low-temperature toughness is somewhat sacrificed, it still meets the usage conditions. This represents a revolutionary update in understanding for mining equipment designers.

[0039] The dry friction wear rate of the Al4% sample was as low as 4.38 × 10⁻⁶. -5 mm 3 / (N·m), a 51.5% reduction compared to Al-free steel, significantly exceeding the reasonable expectations of those skilled in the art. This magnitude of increase in wear resistance cannot be derived solely from conventional solid solution strengthening and grain refinement effects; it involves a synergistic mechanism by which Al promotes the formation of a dense oxide film on the surface, which is technically unpredictable.

[0040] Conventionally, the tempering temperature of medium-manganese steel depends primarily on the target strength level, rather than having a strict negative correlation with the content of a single alloying element. This invention, through extensive experimental research, has discovered that the higher the Al content, the lower the tempering temperature must be—a counterintuitive finding (high alloying typically requires higher tempering temperatures to promote carbide dispersion). This original finding provides theoretical support at the process level for the precise control of the performance of gradient aluminum medium-manganese steel, constituting a paradigm of integrated composition-process synergistic innovation.

[0041] The embodiments proposed in this invention are preferred embodiments, but are not limited to the content described above. Those skilled in the art can easily replicate the above embodiments and further extend and modify them, but as long as they do not depart from the spirit of this invention, they are all within the protection scope of this invention.

Claims

1. A gradient aluminum-manganese steel adapted for mining conditions, characterized in that, Its chemical composition, by mass percentage, includes: C: 0.25~0.35%, Mn: 5.5~8.5%, Si: 0.4~0.8%, P≤0.01%, S≤0.01%, Al: 0.8~4.5%, balance being Fe and unavoidable impurities; The Al content is differentially controlled within three gradient ranges from 0.8% to 4.5%. By differentiating the mechanical properties, wear resistance, and corrosion resistance of the steel body through different Al content ranges, the performance of different service components in the mine can be targeted and matched.

2. The gradient aluminum-manganese steel adapted for mining conditions according to claim 1, characterized in that: When the Al content is 0.8~1.2%, the steel body is suitable for mining bucket sidewall components that require high strength-plasticity balance and low-temperature toughness.

3. The gradient aluminum-manganese steel adapted for mining conditions according to claim 1, characterized in that: When the Al content is 1.8~2.2%, the steel body is suitable for mine support components that require high synergistic performance in low-temperature toughness and impact wear resistance.

4. The gradient aluminum-manganese steel adapted for mining conditions according to claim 1, characterized in that, When the Al content is 3.8~4.5%, the steel body is suitable for mining bucket cutting edge components that require high strength, high wear resistance and high corrosion resistance.

5. The mine-condition-adaptive gradient aluminum-manganese steel according to any one of claims 1 to 4, characterized in that: Meet at least one of the following performance metrics: Tensile strength ≥ 877 MPa; Yield strength ≥ 521 MPa; Elongation after fracture ≥26%; Dry sliding friction wear rate at 200N ≤ 7.64×10 -5 mm 3 / (N·m); Charpy V-shaped impact energy at -40℃ ≥41 J; The corrosion weight loss rate after 48 hours of salt spray corrosion was lower than that of aluminum-free medium manganese steel.

6. A method for preparing a mine-condition-adaptive gradient aluminum manganese steel according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Smelting and Composition Control: The amount of aluminum ingots added is precisely controlled according to the target Al content. After electric furnace smelting, LF furnace refining and vacuum treatment, with a vacuum degree ≥70kPa and a holding time ≥30 min, the Al element is evenly distributed in the molten steel. S2, Gradient Adaptive Rolling: The billet is placed in a regenerative heating furnace, preheated to 850℃ at a rate of ≤85℃ / h, and then heated to 1150~1160℃ and held for 2~4 hours. It is then rolled in the high-temperature austenitic region with an initial rolling temperature ≥1090℃ and a final rolling temperature ≥920℃. The austenitic grains are refined by temperature and rolling control. S3, Performance-Targeted Heat Treatment: Quenching temperature ≥ 850℃, cooling to < 100℃ and exiting water with reddening temperature < 200℃; The tempering temperature should be adjusted according to the Al content, and the temperature should be maintained for 4-8 hours before air cooling to room temperature. The principle for adjusting the tempering temperature is: the higher the Al content, the lower the tempering temperature.

7. The preparation method according to claim 6, characterized in that, The tempering temperature mentioned in step S3 is: When the Al content is 0.8~1.2%, the tempering temperature is 200~220℃; When the Al content is 1.8~2.2%, the tempering temperature is 190~210℃; When the Al content is 3.8~4.5%, the tempering temperature is 170~190℃.

8. The preparation method according to claim 6, characterized in that: The vacuum treatment in step S1 has a vacuum degree of ≥70kPa and a holding time of ≥30 min, which is used to remove gas and trace impurities from the molten steel and promote the uniform distribution of Al elements in the steel matrix, avoiding the formation of inclusions and agglomeration under high Al content.

9. The preparation method according to claim 6, characterized in that, The heating rate of the preheating section in step S2 is controlled at ≤85℃ / h to prevent the billet from cracking due to thermal stress and to ensure the uniformity of the microstructure of the high Al content steel body.

10. The application of the mining-condition-adaptive gradient aluminum-manganese steel according to any one of claims 1 to 4 in key components for multiple mining conditions, characterized in that, The key components for various working conditions in the mine are the liners of the mine crushing equipment, the cutting edge of the bucket of the shovel and conveying equipment, or the mine support frame.

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